The germination of fungal spores may be used as a convenient experimental system for study of mitochondrial biogenesis and participation of mitochondrial genetic functions in cellular development. Ungerminated, dormant spores of the mycelial fungus Botryodiplodia theobromae contain mitochondria which do not have the well-developed respiratory system of rapidly-growing germinated spores. The general objective of this proposed project is to study the respective biochemical contributions of the nuclear genetic system and the rudimentary, semi-autonomous genetic system of the mitochondria in the assembly and function of these organelles as the fungal spores undergo highly-synchronized germination. As an indicator of mitochondrial genetic activity, the developing respiratory system will be characterized with respect to the kinetics of oxygen uptake during germination, the qualitative and quantitative cytochrome content of the mitochondria, and the functional response of the developing respiratory system to treatment of the spores with inhibitors of the nuclear and mitochondrial genetic systems. The nature and genetic origins of proteins assembled into the mitochondria during germination will be studied by gel electrophoretic analysis of several proteins whose syntheses are believed to occur at least in part on mitochondrial ribosomes, and radioactive precursor labelling studies (in the presence and absence of chemical inhibitors) will be performed to measure the kinetics of synthesis and sequence of assembly of new proteins into the mitochondria after translation on cytoplasmic or mitochondrial ribosomes.